1. Field of the Invention
The present invention relates to an image forming apparatus including a scanner and a printer, which can combine a digital image with an image indicating a content handwritten by a user.
2. Description of the Related Art
A recent multifunction peripheral (MFP) which includes a printer capable of printing an image on a sheet and a scanner capable of reading the sheet could perform various operations. For example, as discussed in Japanese Patent Application No. 2003-80789, the multifunction peripheral can combine a digital image stored in a storage medium with a scanned image read by a scanner from a handwritten sheet (hereinafter, referred to as a “handwritten image”) and print the combined image.
More specifically, the multifunction peripheral causes the printer to print a sheet on which a user can add information by handwriting (hereinafter, referred to as a “handwritten document sheet”) and causes the scanner to read the sheet after the user completes an entry by handwriting. Then, the apparatus extracts the handwritten image from the scanned image and combines the extracted handwritten image with the digital image. The user is allowed to add a handwritten image in a specific area (hereinafter, referred to as a “handwriting area”) on the handwritten document sheet. Further, the digital image in the storage medium (i.e., the image designated as an object to be combined with the handwritten image in the handwriting area of the handwritten document sheet) is referred to as a “combination target image” or a “background image.”
Further, the multifunction peripheral has a function of printing a pale image of the combination target image (hereinafter, referred to as a “pale printed image” or a “reference image”) in the handwriting area to guide the user to add the handwritten image to a desired position on the combination target image when they are combined.
However, to realize the above-described guiding function, the multifunction peripheral is required to discriminate a pale printed image from a handwritten image to accurately extract the handwritten image from the handwriting area. Meanwhile, it is desired that the users are allowed to use various colors for the entry by handwriting. However, if the color of a handwritten content has a higher luminance value, it is difficult to discriminate the pale printed image from the handwritten image.
In this respect, Japanese Patent Application No. 2007-243529 discusses an image forming method that prints a color patch on a handwritten document sheet that indicates a color used for a pale printed image. More specifically, the method analyzes image data obtained from a handwriting area of the sheet and compares the used color with the color patch to discriminate the pale printed image from the handwritten image.
However, according to this method, it is necessary to prepare the patch for discriminating the pale printed image beforehand somewhere on the handwritten document sheet. In other words, providing a patch at a specific position on the handwritten document sheet restricts the design of the handwritten document sheet.